1. Field of the Invention
The invention relates to an energy transfer device for carrying out wireless transfer of energy without the use of electrical wires and the like.
2. Description of the Related Art
The US 2006/0113955 A1 discloses a wireless charging and power system for electronic devices and a method for communicating power to a power receiver employing wireless energy transmission. The remote charging system includes a power transmission unit which transmits energy as a plurality of constructive transmitted frequencies and a power receiver system that receives the transmitted frequencies. The power receiver is preferably incorporated in a device and includes an energy receptor capable of receiving the wireless transmitted energy and transferring the energy from the transmitted frequencies to an energy storage device included in the device.
The EP 1 022 840 A2 discloses a controller for a battery charger which inductively supplies electrical power for charging a battery in a mobile device. The battery charger includes a self-oscillating power oscillator with at least one separate resonance circuit in the output circuit. The mobile device contains at least one resonance circuit in the inductive coupling section. To detect the coupled mobile device, the controller of the battery charger periodically changes the oscillation frequency of the oscillator during a short test duration and monitors a resulting change in the oscillator operating current. Therefore, any possible changes in the operating current of the oscillator due to the reaction of the resonance circuit of a possibly coupled mobile device is observed to determine the presence of such device.
For example, Japanese Patent Application Publication No. 2008-22429 (JP-A-2008-22429) describes a system for carrying out energy transfer by transmitting electromagnetic waves of a predetermined frequency from a power transmission antenna, receiving the transmitted electromagnetic waves with a receiving antenna and extracting the electric power.
However, this type of wireless energy transfer system has the problem of the energy that is transferred easily stolen. For example, a person desiring to steal energy can receive electromagnetic waves transmitted from a power transmission antenna and steal electric power by preparing an antenna having a predetermined resonance frequency for use as a receiving antenna for stealing electric power and then arranging the receiving antenna for stealing electric power at a predetermined location. In this case, since energy is not being transferred by electrical wires and the like, connection of electrical wires and the like is not required, thereby enabling energy to be stolen easily.
In this case, although it may be possible to detect the theft of electrical power based on whether or not a receiving antenna for stealing electric power is installed, this requires an object detection device that detects the installation of a receiving antenna for stealing electric power, and the detection of the theft of electric power is not easy.